Control switch



Nov. 10, 1953 w. H. HOLLINSHEAD CONTROL SWITCH 2 Sheets-Sheet 1 Filed July 28, 1950 INVENTOR. W/ZZ/fl/V /7 H011 M42754 l9 TTORNE 1953 w. H. HOLLINSHEAD CONTROL SWITCH 2 Sheets-Sheet 2 Filed July 28, 1950 Fly;

ATTORNEY Patented Nov. 10, 1953 UNITED STATES PATENT OFFICE CONTROL SWITCH William H. Hollinshead, St. Paul, Minn.

Application July 28, 1950, Serial No. 176,362

8 Claims. 1

The invention herein presents a control switch, actuable to closed condition in response to decrease in fluid pressure and to open condition in response to increase in fluid pressure, useful for many purposes, but devised to be especially useful in the control of electrical circuits including motors for actuating pumps employed to build up pressure in fluid pressure systems.

The object of the invention is to provide a pressure controlled switch wherein will be incorporated various novel and improved features and characteristics of construction.

In the accompanying drawings forming a part of this specification,

Fig. 1 is a central sectional view of a control switch made according to the invention as when in open condition;

Fig. 2 is an elevational view, on a reduced scale, of a first unit of the control switch removed from the remainder thereof, as said first unit would appear from the right in Fig. 1;

Fig. 3 is a view corresponding generally with the disclosure of Fig. 1, but showing the control switch in closed condition;

Fig. 4 is a perspective view of a second unit of the control switch removed from the remainder thereof;

Fig. 5 is a sectional view, on a reduced scale, taken on line 5-5 in Fig. 3;

Fig. 6 is a sectional view, taken on line 6-6 in Fig. 4, or as on line 66 in Fig. 5;

Fig. 7 is an elevational view, on a reduced scale, of a frame of the control switch as it would appear from the right in Figs. 1 and 3; and

Fig. 8 is an elevational view of a disc shape element of the control switch.

With respect to the drawings and the numerals of reference thereon, I denotes a frame, I I represents a first unit and I2 indicates a second unit of a control switch incorporating features and characteristics of the invention.

The frame I0 consists of a rectilinear member including an end wall I3 and opposite, spaced, parallel side walls I4, I4 perpendicular to said end wall I3. A removable cover I encloses an open side of the frame I0 adjacent the end wall l3 and an open end of said frame opposite said end wall, and an open side of said frame adjacent its end wall and opposite the portion of the cover adjacent said end wall is enclosed by a flat plate I6 constituted as a part of the first unit I I of the control switch.

The flat plate I6 includes inwardly turned flanges I! at its opposite sides which receive screws I8 rigidly attaching said flat plate to the frame I0, and also includes an inwardly turned flange I9 at its end opposite the end wall I3 of said frame. The removable cover I5 includes inwardly turned flanges fitted over the adjacent edges of the end and side walls of the frame, and a marginal edge portion of said removable cover, at its end opposite the frame end wall, is fitted over the inwardly turned flange I9 and includes a slot 20 which removably receives a screw 2| in said inwardly turned flange I9 for detachably securing the removable cover on said frame.

An intermediate portion of the flat plate I6 is shaped inwardly to provide an annular concavity 22 in the outer side of said flat plate, and a disc shape element 23 in said concavity includes spaced, parallel actuator lugs 24 which are in right angular relation to the body of said disc shape element and extend through an elongated slot 25 in a portion of said flat plate I6 bounding the concavity 22. As disclosed, the spaced actuator lugs 24 are in a plane spaced from and parallel with the end wall I3 of the frame I0.

A cap member 26, at the outer side of the flat plate I6 and its annular concavity 22, is secured up against said flat plate by a series of screw bolts 21 which also secure a flexible diaphragm 28, of rubber as disclosed, across said annular concavity and a central hollowed-out portion of said cap member in such manner as to provide a chamber 29, bounded by the cap member and said flexible diaphragm, disposed at the outer side of and in alinement with the annular concavity 22. An inlet, from a source (not shown) of fluid under pressure, to the chamber 29 is indicated 30, and except for said inlet said chamber is closed.

A support member of the first unit II of the control switch consists of a flat piece 3I of metal with annular opening 32, spaced bearing lugs 33 struck up from said flat piece 3| at locations contiguous with said annular opening, and spaced flange portions 34, struck up from the flat piece at locations contiguous with marginal portions thereof, providing stops 35 in spaced relation to said flat piece and in a plane spaced from and parallel with the plane in which the bearing lugs 38 are situated. The flat piece 3| of the support member is secured up against an inner surface of the flat plate I6, with the bounding surface of the annular opening 32 in spaced, surrounding relation to the actuator lugs 24 and surrounding relation to the inwardly shaped portion of the flat plate, by the screw bolts 21 which secure the cap member 26, the flexible diaphragm 28 and the flat plate to each other, and when said support member is in assembled position, the bearing lugs A transverse pivot pin 36, extending between the bearing lugs 33 and having its opposite end portions mounted therein, rotatably supports a first actuator lever 31, situated between said hearing lugs, an adjuster lever 33, situated exteriorly of the bearing lugs, and a tension spring 39, situated exteriorly of said bearing lugs and interiorly of said adjuster lever.

The first actuator lever 3'! is constituted as a flat element, having flanges 40 upon the opposite side edges thereof and in perpendicular relation thereto, cut away to provide a clearance opening 4| at an intermediate portion thereof, an actuator and adjuster piece 42 at one end thereof and an actuator piece 43 at the opposite end thereof. The transverse pivot pin 36 is mounted in portions of the flanges 43 which are adjacent an end of the actuator and adjuster piece 42 opposite the actuator piece 43, and said actuator and adjuster piece 42 includes spaced indentations 44, in its surface adjacent the flat piece 3| of the support member and in spaced relation to the transverse pivot pin 36 at the side thereof adjacent said actuator piece 43, which receive the free end portions of the actuator lugs 24 upon the disc shape element 23. Stated differently, in practical operation of the control switch, the free ends of said actuator lugs 24 are engaged against the bounding surfaces of the indentations 44.

The adjuster lever 38 is of U -shape. It includes a base 45, in adjacent relation to the fiat piece 3| of the support member at a location spaced from the bearing lugs 33 at the side thereof opposite the actuator lugs 24 and the stop 35, and legs 46 rotatably mounted on the transverse pivot pin 35. A first adjuster screw 41, in spaced, parallel cars 48 integral with the base 45 of the adjuster lever 38, has its free end engaged against the adjacent surface of the flat piece 3| of the support member and includes an accessible head 49 through the instrumentality of which said first adjuster screw can be readily and easily turned thus to swingingly adjust said lever 38 toward or away from said fiat piece 3|.

The construction and arrangement are such that when the first actuator lever 31 is assembled with the transverse pivot pin 33, the actuator piece 43 is situated at the side of the flange portions 34 opposite the bearin lugs 33 and inwardly of the stops adjacent the flat piece 3| of the support member, to engage said stops 35 in response to swinging movement of said actuator piece away from said flat piece. Stated otherwise, the first actuator lever 3! is mounted for swinging movement toward and away from the flat piece 3| of the support member, and the stops 35 limit the extent to which said first actuator lever can be swung away from said flat piece,by reason of engagement of the actuator piece 43 with said stops. Also, portions of the flanges 4!] of the first actuator lever 31 which are adjacent said actuator piece 43 are disposed exteriorly of the flange portions 34 and the stops 35 of the support member when said first actuator lever is assembled with said transverse pivot pin.

The tension spring 39 consists of a length of wire of U-shape including a base 53 and spaced, parallel arms Each arm 5| includes a curl or loop 52 intermediate its ends which is rotatably supported upon the transverse pivot pin 36. Portions of said arms 5| adjacent the base 50 are engaged against the adjacent edge of the base 45 of the adjuster lever 38, and free end portions of the arms 5|, at the side of said transverse pivot p 33 opposite the bases and 53, are seated against surfaces of ears 53, extending externally from portions of the flanges 4|! of the first actuator lever 31 adjacent the opposite ends of the actuator piece 43, which are opposite the flat piece 3| of the support member. The construction and arrangement are such that the tension spring 39 normally resiliently urges portions of the flanges 40 of the first actuator lever 3'! which are adjacent said actuator piece 43 into engaged relation with the adjacent surface of the flat piece 3| of the support member. The tension under which said first actuator lever 31 is urged toward and against said flat piece of said support member is adjustable in response to manipulation of the first adjuster screw 47. With turning of said first adjuster screw in direction to cause the base 45 of the adjuster lever 38 to be moved away from the flat piece 3|, the tension of the spring 39 against the ears 53 will be increased, and vice versa.

A second actuator lever of the first unit ll of the control switch is denoted 54. Said second actuator lever consists of a U-piece of flat metal including a more or less tapered base 55 and spaced legs 56. Outer edges of end portions of the legs 55 spaced from the base 55 integrally support exteriorly extending trunnions 51 situated in and rotatabl seated against the bounding surfaces of grooves 58 in marginal edges of the flange portions 34 upon the flat piece 3| of the support member which are at the side of said flange pertions adjacent the transverse pivot pin 36, and a tension coil spring 59, disposed in a space between the legs 56, has one of its ends secured, as at 60, to a central portion of the actuator piece 43 and its other end secured, as at El, to a central portion of the tapered base 55, thus to retain the trunnions 5'! in seated position against the bounding surfaces of the grooves 58.

The construction and arrangement are such that the tension coil spring 59 retains the end portion of the tapered base 55 of the second actuator lever 54 spaced from the trunnlons 51 in engaged relation with an adjacent surface of the inwardly shaped portion of the flat plate It, as in Fig. 3 of the drawings, when the first actuator lever 3! is retained in normal position, dictated by the tension spring 39. The construction and arrangement also are such that said second actuator lever 54 will be swung away from said flat plate l8, from left to right in said Fig. 3, with a snap action in response to swinging movement of said first actuator lever away from the flat piece 3| of the support member, also toward the right in Fig. 3, to extent sufficient to situate the actuator piece 43 outwardly with respect to the axis of the second actuator lever to cause the tension coil spring 59 to be swung outwardly beyond dead center position for said second actuator lever. That is, when the parts are in normal position, said actuator piece 43 is situated at the inner side of said second actuator lever axis to cause said tension coil spring to be at the inner side of dead center position for the second actuator lever thus to cause it to be retained in an inward position, and with outward swinging movement of the actuator piece 43 it becomes situated at the outer side of the second actuator lever axis to cause the tension coil spring to be at the outer side of dead center position for said second actuator lever thus to cause it to be swung to and retained in an outward position.

A stop for limiting the extent to which the second actuator lever 54 can be swung by the tension coil spring 59 away from the flat plate I6 is constituted as a second adjuster screw 62 in the actuator and adjuster piece 42 of the first actuator lever 3? adapted to be engaged, as disclosed in Fig. l of the drawings, by the tapered base 55 of said second actuator lever. A head es of the second adjuster screw 52 is conveniently accessible in order that adjustment of the extent to which the second actuator lever 54 is capable of swinging away from the support member can be readily and easily accomplished.

An insulating block 6d of the second unit E2 of the control switch is suitably and conveniently rigidly supported upon and between the side walls M of the frame Hi, as by rectilinear protuberances 65 upon opposite ends of said insulating block inserted in rectilinear openings 66 in said side walls, to be situated in spaced, adjacent relation to the first unit I l at the side thereof opposite the inlet Bil.

Spaced apart, fixed contact elements 51 upon the insulating block 8c are adapted to receive lead wires (not shown) of an electrical circuit includin a motor, as for operating a pump for building up pressure in a fluid pressure system. As disclosed, there are two sets of fixed contact elements Ell. Each of separate movable contact elements, for bridging the contact element 61 of each set of fixed contact elements, is represented 63, and a compression coil spring 69, of consider ably less strength than the tension coil spring so, normally urges each movable contact element iiil into engagement with a pair of fixed contact elements 6'7. The movable contact elements 68 are situated in concavities m of the insulating block fit, interiorly of the fixed contact elements 6! and in facing, spaced, parallel relation to the fiat plate it of the first unit H, and the compression coil springs 59 are disposed in said concavities is interiorly of said movable contact elements. As disclosed, each compression coil spring 59 has one of its end portions seated in a pocket I! contiguous with a corresponding concavity it and its opposite end engaged against a central portion of the adjacent surface of a corresponding movable contact element 58, thus to resiliently urge the movable contact elements into engaged. relation with the fixed contact elements 6?. will be such that when the movable contact elemerits E8 bridge the two sets of fixed contact elements til the circuit including said fixed contact elements will be closed, and when said movable contact elements are disengaged from the fixed contact elements said circuit will be broken.

An actuator is, for causing the movable contact elements 68 to be removed or separated from the fixed contact elements 61, consists of a fiat strip of insulating material slidably disposed in spaced slots #3, at the opposite sides of the com cavities Hi and in contiguous relation to said movable contact elements 53, and having spaced protuberances M upon its interior end situated in perforations 15 through central portions of the diiierent movable contact elements. A central part of the interior end portion of the actuator i2 is cut away, as at E6, to be clear of a projection l1 upon the insulating block 64 between its concavities it, and a central part of the exterior end of said actuator 12 is provided with a partcircular clearance opening 18.

The construction and arrangement are such that when the parts of the first unit H of the The construction and arrangement 0 control switch are in their normal position, as in Figs. 3 of the drawings, with the first actuator lever 31 retained by the tension spring 39 against the flat piece 3! of the support member and the second actuator lever 54 retained by the tension coil spring 59 against the inwardly shaped portion of the fiat plate It, said second actuator lever is in clearing relation to the adjacent end of the actuator 12 thus to permit the compression coil springs S9 to retain the movable contact elements 63 in engaged relation with the fixed contact elements Bl. In said Fig. 3, all of the operative parts of the control switch are dis-' closed as when pressure in the chamber 29, and hence in the system, is below an intended pressure, thus to cause an electric motor in circuit with said fixed and movable contact elements to be operative to actuate a pump adapted to cause pressure to be built up in said system and chamher.

The flexible diaphragm 28 will be forced from its positioin as in Fig. 3 toward its position as in Fig. 1 in response to build up of pressure in the system, and hence in the chamber 29, thus to cause the first actuator lever 31 to be swung from its position as in said Fig. 3 toward its position as in said Fig. 1, through the instrumentality of the disc shape element 2s and against force exerted by the tension spring es, and upon the swinging of said first actuator lever til away from the fiat piece SI of the support member, toward the second unit l2 of the control switch, to extent sufficient to situate the actuator piece d3 outwardly with respect to the axis of the second actuator lever 54 to cause the tension coil spring 59 to be swung outwardly beyond dead center position for said second actuator lever, the latter will be swung with a snap action, from its position as in Fig. 3 to its position as in Fig. 1, against the stop or second adjuster screw 62. The construction and arrangement will be such that the spaced legs 56 of the second actuator lever 54 will strikingly engage the adjacent end of the actuator '12, while the tension coil spring 59 enters the clearance opening 18, thus to cause the movable contact elements cc to be forcibly removed from the fixed contact elements e1, during snap action movement of said second actuator lever from its position as in Fig. 3 to its position as in Fig. l, and as long as pressure of fluid in the chamber 29, and hence in the system, remains sufiiciently high to retain the first actuator lever ill in position situating the second. actuator lever 5d at the outer side of its dead center position, said second actuator lever will retain said fixed and movable contact elements in disengaged relation. Upon decrease of pressure of fluid in the system, and hence in the chamber 29, to a value sumciently low to permit the ten sion spring 39 to actuate the first actuator lever 31 to situate the second actuator lever 54 at the inner side of its dead center position, said second actuator lever will be swung with a snap action from its position as in Fig. 1 back to its position as in Fig. 3, thus to cause the fixed and movable contact elements to become engaged.

It will be apparent that the pressure of fluid in the chamber as, and hence in the system, necessary to actuate the operating elements of the control switch to cause building up of pressure of fluid to cease will be proportional to the ten sion of the spring 39. With increase in tension of said spring, the pressure of fluid required to cause the fixed and movable contact elements 6? and 63 to be disengaged will be increased, and

vice versa. The tension of the spring 39 operative upon the first actuator lever 31 to resiliently urge it in direction toward the fiat piece CH of the support member is capable of being nicely adjusted merely by turning adjmtrnent of the first adjuster screw 4?, thus to adjust the lever 38 away from said flat piece to cause the tension of the spring 39 to be increased and toward the fiat piece to cause the tension of said spring 32 to be decreased. The first adjuster screw 41 is in practice an instrumentality for initially accomplishing sensitive adjustment of the control switch rendering it capable of shutting off fluid pressure building up power when the pressure of fluid in a fluid pressure system has reached any high value which may be predetermined.

With return movement of the first actuator lever 31 from its position. as in 1 toward its position as in Fig. 3, in response to decrease of pressure in the chamber 25*, and hence in the system, the base @555 of the second actuator lever 54 obviously will be swung in direction to correspond, through the instrumentality of the stop or second adjuster screw which is at this time engaged with said base concuu'ently with the swinging of the actuator piece of said first actuator lever to and past dead center position for said second actuator lever. It will be appar cut that when said stop or second adjuster screw 62 is situated in the actuator and adjuster iece 42 of the first actuator lever M to permit outward throw of said second actuator lever beyond its dead center position to be relatively great,

the return movement of said first actuator lever 3'! required to cause the second actuator lever 54 to be swung inwardly toward the flat plate It beyond its dead center position necessaril will have to be through a longer are than when the outward throw of the second actuator lever is comparatively less. Stated otherwise, when the second adjuster screw 62 is situated in the actuator and adjuster piece it of the first actuator lever 31 to arrest movement of the second actuator lever 54 at the end of a longer outward throw beyond dead center position, the return movement of said first actuator lever required to move said second actuator lever inwardly beyond its dead center position necessarily will have to be greater in extent than when said second adjuster screw 52 is situated in said actuator and adjuster piece 42 to arrest movement of the second actuator lever at the end of shorter outward throw. Inasmuch as the arc of return movement of the first actuator lever a l is a function of, or proportional to, pressure existent in the system and chamber 29, the second actuator lever 54 obviously will be operated to release the movable contact elements 68 so they can engage the fixed contact elements, by reason of force exerted by the compression coil springs 69, in response to lower pressure in said chamber 29 when the sec-- ond adjuster screw 62 is set in a receded position, so that the free end of said second adjuster screw is closer to the actuator and adjuster piece 42, than when set in an advanced position, so that the free end of the second adjuster screw is farther from said actuator and adjuster piece. The second adjuster screw 54 is in practice an instrumentality for initially accomplishing sensi tive adjustment of the control switch rendering it capable of turning on fluid pressure building up power when the pressure of fluid in a fluid pressure system has reached any low value which may be predetermined.

What is claimed is:

1. In a control switch, a support, a flexible diaphram mounted on said support to be subjected to fluid under pressure, a first actuator lever, means rotatably mounting said first actuatorlever on said support for swinging movement, first ten sion means constituted as a rotatably supported length of resilient material engaged with said first actuator lever urging the first actuator lever toward the flexible diaphragm, means for accomplishing rotatable adjustment of said length of resilient material thus to adjust the tension under which the first tension means is capable of urging the first actuator lever toward said flexible diaphragm, a device between and engaged with said flexible diaphragm and said first actuator lever operable in response to increase of fluid pressure upon the flexible diaphragm to swing the first actuator lever in direction away from said flexible diaphragm against force of the first tension means, said first tension means being adapted to swing said first actuator lever and device in direction toward said flexible diaphragm in response to decrease in fluid pressure upon the flexible diaphragm, a second actuator lever, means rotatably mounting said second actuator lever on said support at a location adjacent a portion of the first actuator lever spaced from its mounting means for swinging movement toward and away from the flexible diaphragm and to extend in overlying relation to said first actuator lever toward the mounting means therefor, second tension means connecting a portion of said second actuator lever spaced from its mounting means with a portion of said first actuator lever spaced from its mounting means and disposed at the side of the location where said second tension means is connected with the second actuator lever opposite the mounting means for said first actuator lever for causing said sec- 0nd actuator lever to be swung away from said flexible diaphragm in response to movement of the location Where said second tension means is connected to said first actuator lever in direction away from said flexible diaphragm to extent causing the second tension means to become situated at the side of dead center position for the second actuator lever opposite said flexible diaphragm and to be swung toward said flexible diaphragm in response to movement of said location where said second tension means is connected to the first actuator lever in direction toward the flexible diaphragm to extent causing said second tension means to become situated at the side of dead center position for the second actuator lever adjacent the flexible diaphragm, and stop means for limiting the extent of swinging movement of said second actuator lever in either direction.

2. The combination as specified in claim 1, wherein said means for accomplishing rotatable adjustment of said length of resilient material includes an accessible rotatably adjustable element.

3. In a control switch, a support, a flexible diaphragm mounted on said support to be subjected to fluid under pressure, a first actuator lever, means rotatably mounting said first actuator lever on said support for swinging movement, first tension means urging the first actuator lever toward the flexible diaphragm, a device between and engaged with said flexible diaphragm and said first actuator lever operable in respons to increase of fluid pressure upon the flexible diaphragm to swing the first actuator lever in direction away from said flexible diaphragm against force of the first tension means, said first tension means being adapted to swing said first actuator lever and device in direction toward said flexible diaphragm in response to decrease in fluid pressure upon the flexible diaphragm, a second actuator lever, means rotatably mounting said second actuator lever on said support at a location adjacent a portion of the first actuator lever spaced from it mounting means for swinging movement toward and away from the flexible diaphragm and to extend in overlying relation to said first actuator lever toward the mounting means therefor, second tension means connecting a portion of said second actuator lever spaced from its mounting means with a portion of said first actuator lever spaced from its mounting means and disposed at the side of the location where said second tension means is connected with the second actuator lever opposite the mounting means for said first actuator lever for causing said second actuator lever to be swung away from said flexible diaphragm in response to movement of the location where said second tension means is connected to said first actuator lever in direction away from said flexible diaphragm to extent causing the second tension means to become situated at the side of dead center position for the second actuator lever opposite said flexible diaphragm and to be swung toward said flexible diaphragm in response to movement of said location where said second tension means is connected to the first actuator lever in direction toward the flexible diaphragm to extent causing said second tension means to become situated at the side of dead center position for the second actuator lever adjacent the flexible diaphragm, and stop means for limiting the extent of swinging movement of said second actuator lever in either direction, the stop means for limiting the extent of swinging movement of the second actuator lever away from the flexible diaphragm being adjustable toward and away from second actuator lever.

4. In a control switch, a support, a flexible diaphragm mounted on said support to be subjected to fluid under pressure, a first actuator lever, means rotatably mounting said first actuator lever on said support for swinging movement, first tension means urging the first actuator lever toward the flexible diaphragm, a device between and engaged with said flexible diaphragm and said first actuator lever operable in response to increase of fluid pressure upon the flexible diaphragm to swing the first actuator lever in direction away from said flexible diaphragm against force of the first tension means, said first tension means being adapted to swing said first actuator lever and device in direction toward said flexible diaphragm in response to decrease in fluid pressure upon the flexible diaphragm, a second actuator lever, means rotatably mounting said second actuator lever on said support at a location adjacent a portion of the first actuator lever spaced from its mounting means for swinging movement toward and away from the flexible diaphragm and to extend in overlying relation to said first actuator lever toward the mounting means therefor, second tension means connecting a portion of said second actuator lever spaced from its mounting means with a portion of said first actuator lever spaced from its mounting means and disposed at the side of the location where said second tension means is connected with the second actuator lever opposite the mounting means for said first actuator lever for causing said second actuator lever to be swung away from said flexible diaphragm in response to movement of the location where said second tension means is connected to said first actuator lever in direction away from said flexible diaphragm to extent causing the second tension means to become situated at the side of dead center position for the second actuator lever opposite said flexible diaphragm and to be swung toward said flexible diaphragm in response to movement of said location where said second tension means is connected to the first actuator lever in direction toward the flexible diaphragm to extent causing said second tension means to become situated at the side of dead center position for the second actuator lever adjacent the flexible diaphragm, and stop means for limiting the extent of swinging movement of said second actuator lever in either direction, the stop means for limiting the extent of swinging movement of the second actuator lever away from the flexible diaphragm being supported by the first actuator lever for adjustment toward and away from said second actuator lever.

5. In a control switch, a support, a flexible diaphragm mounted on said support to be subjected to fluid under pressure, a first actuator lever, means rotatably mounting said first actuator lever on said support for swinging movement, first tension means urging the first actuator lever toward the flexible diaphragm, a device between and engaged with said flexible diaphragm and said first actuator lever operable in response to increase of fluid pressure upon the flexible diaphragm to swing the first actuator lever in direction away from said flexible diaphragm against force of the first tension means, said first tension means being adapted to swing said first actuator lever and device in direction toward said flexible diaphragm in response to decrease in fluid pressure upon the flexible diaphragm, a second actuator lever, means rotatably mounting said second actuator lever on said support at a location adjacent a portion of the first actuator lever spaced from its mounting means for swinging movement toward and away from the flexible diaphragm and to extend in overlying relation to said first actuator lever toward the mounting means therefor, second tension means connecting a portion of said second actuator lever spaced from its mounting means with a portion of said first actuator lever spaced from its mounting means and disposed at the side of the location where said second tension means is connected with the second actuator lever opposite the mounting means for said first actuator lever for causing said second actuator lever to be swung away from said flexible diaphragm in response to movement of the location where said second tension means is connected to said first actuator lever in direction away from said flexible diaphragm to extent causing the second tension means to become situated at the side of dead center position for the second actuator lever opposite said flexible diaphragm and to be swung toward said flexible diaphragm in response to movement of said location where said second tension means is connected to the first actuator lever in direction toward the flexible diaphragm to extent causing said second tension means to become situated at the side oi dead center position for the second actuator lever adjacent the flexible diaphragm, and stop means for limiting the extent of swinging movement of said second actuator lever in either direction, the stop means for limiting the extent of swinging stat-am 11 movement of the second actuator lever away from the fiexible diaphragm being constituted as an accessible element rotatably adjustable in the first actuator lever for movement toward and away from said second actuator lever.

6. The combination as specified in claim 3, and means for adjusting the tension under which said first tension means is capable of urging said first actuator lever toward said flexible diaphragm.

7. The combination as specified in claim 4 wherein said first tension means is constituted as a rotatably supported length of resilient mate rial engaged with said first actuator lever, and means for accomplishing rotatable adjustment of said length of resilient material thus to adjust the tension under which the first tension means is capable of urging said first actuator lever toward said flexible diaphragm.

8. The combination as specified in claim 5 wherein said first tension means is constituted as a rotatably supported length of resilient ma: terial engaged with said first actuator lever, and means for accomplishing rotatable adjustment of said length of resilient material thus to adjust the tension under which the first tension means is capable of urging the first actuator lever toward said diaphragm, said last mentioned means including an accessible rotatably adjustable element as a part thereof.

WiLLIAM H. HOLLINSHEAD.

References Cited in the file of this patent UNITED STATES PATENTS 15 Number Name Date 2,020,485 Van Valkenburg Nov. 12, 19-35 2,281,544 Beeman et a1. May 5, 1942 2,307,265 Hansen Jan. 5, 1943 2,469,119 Koertge May 3, 1949 

